Crucial, unreleased video implicates Dzhokhar Tsarnaev

Video from a restaurant surveillance camera shows Dzhokhar Tsarnaev walking toward the scene of the second bombing and slipping his backpack off, investigators say. In addition, the FBI says agents searched Dzhokhar Tsarnaev’s dorm room and found a large pyrotechnic as well as BBs, a white hat and a black jacket resembling what was worn in the bombing suspect photos released by the FBI. NBC’s Pete Williams reports.

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>>>good evening. it is a bit hard to believe it's been a week since the bombings in
boston
and yet today ten minutes to 3:00
eastern time
marked a week exactly. in parts of
boston
, you could hear nothing at all. something else happened today. the surviving bomber was charged. and as often happens, the feds came public with details of what they have gathered so far in this investigation that none of us had heard before.
pete williams
has headed up our coverage since first word of the bombing a week ago. he starts us off again tonight from our d.c. newsroom. pete, good evening.

>> reporter: brian, good evening. the government says it has photographic evidence placed the suspect at the scene as well as
physical evidence
tying them to the bombs. we are learning new details about the
car jacking
last thursday that led to a violent shootout in the
boston
suburb of
watertown
. at 2:38 last monday afternoon,
11 minutes
before the first bomb goes off, the
fbi
says, a
surveillance camera
catches dzhokhar and
tamerlan
tsarnaev walking toward the
boston marathonfinish line
with backpacks. a crucial piece of evidence comes from a
surveillance camera
mounted on this restaurant. at 2:42, seven minutes before the first bombing, court records say the video says dzhokhar tsarnaev walked toward the scene of the second bombing. he works his way into into the crowd and slips his backpack off. still photos show the backpack on the ground at his feet. when the first bomb goes off the
fbi
says the video shows the crowd looking toward the
finish line
in alarm. but the
fbi
says tsarnaev virtually alone among the individuals in front of the restaurant appears calm. he walks away, it says, without his backpack. ten seconds later the second bomb goes off in the spot where he left the backpack. the
fbi
says both the marathon bombs were made with
pressure cookers
and contained metal b.b.s coated with adhesive. they contained hobby fuse similar to this. at the scene of thursday night's shootout with the bomb suspects in
watertown
, investigators say they found another bomb made with the same brand of
pressure cooker
and also hobby fuse and bbs. agents searched dzhokhar tsarnaev's college room and found bbs and a large pyrotechnic, a
white hat
and black jacket resembling what was worn by the man in the bombing suspect photos released by the
fbi
. a former
federal prosecutor
said it is a surprisingly solid start.

>>they took unknowns and made it virtually a known a week later. the entire toift
law enforcement
in this case should be commended for their efforts.

>> reporter: court documents contain new details about thursday night's
car jacking
. the
fbi
says surveillance pictures show dzhokhar and
tamerlan
tsarnaev at a
gas station
in cambridge where they drove with the owner of the suv they car jacked. one of them, investigators say, began by pointing a gun at the driver and saying, did you hear about the
boston
explosion? i did that. the car jacker showed the driver he had bullets in the gun and said, i'm serious. at the scene of the shootout in
watertown
where
tamerlan
tsarnaev was killed other explosives were found. in an interview for "
dateline nbc
" the police commissioner said he thinks the brothers planned other attacks.

>>we had to step over unexploded devices they threw at the officers. i can only understand from that that they had other targets. they were going other places.

>> reporter: both charges today carry the
death penalty
as a maximum sentence. it is a long way before p the
justice department
decides to seek it. if it did, he would be, by far, the youngest defendant in a federal
death penalty
case if
modern times
. brian?